Recently, dual-energy CT imaging technology has been playing an importance role in various fields like security inspection, lossless detection and medical treatment, as it can achieve optimal detection accuracy and enable efficient object reconstruction and material identification.
There are currently two primary implementations for a dual-energy CT imaging method. One of the implementations is a pseudo dual-energy system which performs dual-energy imaging with specifically designed double-tiered detectors, as shown in FIG. 1. In the system of FIG. 1, when scanning is performed, rays penetrate through an object and first arrive at the first tier of low-energy detectors. Then, the rays transmit filtering sheets and finally arrive at the second tier of high-energy detectors. At the same time, respective pixels of two resultant transmission images are automatically in correspondence with identical ray paths.
The other implementation is a real dual-energy system which performs circular scanning on an object using ray sources of different energy levels, as shown in FIGS. 2A and 2B. During the first round of scanning shown in FIG. 2A, the object is scanned with rays at a first energy level. Then, the rays are switched from the first energy level to the second energy level. During the second round of scanning shown in FIG. 2B, the object is scanned with rays at the second energy level. The method shown in FIGS. 2A and 2B requires radiation dose and scanning time two times more than a single-scanning method. Image matching is also required between transmission images of low and high energy levels to ensure pixels of the two images at the same coordinate correspond to the same ray path.
In practical applications, the pseudo dual-energy system is more popular than the real dual-energy system, as it can save up to about half of the scanning time period. Unfortunately, the pseudo dual-energy system requires two tiers of detectors for synchronized data collection and thus costs more than the real dual-energy system. This adversely affects the popularization of the pseudo dual-energy system.